Surfactant coatings for surfaces have many utilities including fluid transport, anti-fog coatings, anti-splash coatings, wetting, foam control, and the like. Surfactants can provide a surface with desirable physical or chemical properties not provided by an underlying substrate surface.
For example, certain devices such as diagnostic test devices can be constructed with a substrate made from one or more materials that do not promote transport of fluids such as aqueous solutions to an extent sufficient to provide the device with a desired level of performance, even though the substrate materials provide other desirable qualities to the device. Thus, a surfactant coating on at least a portion of the device can provide physical or chemical properties that promote fluid transport and, therefore, improve performance of the device.
Surfactants can provide a hydrophilic surface to a substrate that promotes fluid transport over a portion of the substrate coated with the surfactant. Such hydrophilic surfaces can be provided by coatings of suitable surfactants. Suitable surfactants include, but not limited to, alkoxylated hydrocarbon alcohols; polyalkylene glycol hydrocarbon ethers and esters; silicone copolyols; polyethoxylated phenols; fatty acid esters of polyalkoxylates such as polyethyelene glycols; fluorochemical surfactants such as polyalkoxylated perfluoroalkyl-containing surfactants as well as anionic perfluoroalkyl-containing surfactants; alkyl, aralkyl and alkaryl anionic surfactants including sulfonates, sulfates, phosphonates and phosphates; and alkyl, aralkyl and alkaryl amphoteric surfactants such as betaines, sultaines, and fatty imidazolines and derivatives thereof. However, many of these surfactants may not be suitable for use in a device that experiences extended storage periods, especially at elevated temperatures and/or in a product construction where reagents, adhesives, dyes, drug and excipients, or other contaminants may exist, because the hydrophilic character provided by the surfactant coating can dissipate over time in storage or, alternatively, at elevated temperatures.
Therefore, a need exists for a surfactant composition useful for forming a coating that is able to provide a hydrophilic surface to a substrate such that the coating is able to promote fluid transport and retains its hydrophilic character to a greater extent than known surfactant coatings.